This invention relates generally to the production of biaxially oriented thermoplastic containers used primarily by beverage bottlers. In particular the present invention relates to the high rate production of such articles from injection molded article preforms.
Biaxially oriented thermoplastic beverage bottles are produced primarily on two types of equipment. The first of these, an integrated machine, combines the preform producing injection molding operation with the bottle producing blow molding operation. Generally, such equipment includes a thermal conditioning apparatus between the injection and blow molding stations to adjust the temperature of the thermoplastic material to a level suitable for blow molding. This thermal conditioning apparatus may perform cooling and reheating of the newly created preforms. Typically, this type of equipment conveys the preforms from the injection molding station throughout the remaining operating stations by clamping and molding apparatus that forms the capping portion of the finished bottle. Consequently, the preform carrying apparatus must be capable of precise positioning and must be sufficiently rigid to permit both injection and blow molding operations.
The second type of equipment operates upon premanufactured preforms and includes apparatus for reheating the preforms to a suitable temperature for molecular orientation during blow molding and further includes apparatus for blow molding. This type of equipment is known as reheat-and-blow machinery. In this type of equipment, the preforms are transferred from carriers to mold sections prior to blowing, a step which requires additional article handling equipment as compared to the integrated type of equipment.
In both types of equipment, a set of bottles is blow molded by closure of a single set of mold sections to surround, at most, one row of preforms. Mold closing actuators operate individually on the mold sections comprising the set, and clamping forces required to overcome the bottle expansion forces are distributed among these actuators. Consequently, the production rate of bottles is limited by the number that can be simultaneously produced by equipment operating on single rows of articles. Because increases in the density of the rows is limited by the bottle size and process forces, higher production rates require lengthening of the rows with the attendant increase in machine volume.
It is therefore one object of the present invention to provide a blow molding means which can simultaneously operate on more than one set of mold sections.
It is a further object of the present invention to minimize the volume required by molding means simultaneously operating on more than one set of mold sections.
It is a further object of the present invention to provide a molding means which can receive and operate on article preforms which are retained by modular carriers which are not susceptible to requirements of precise alignment with molding equipment.